Preparation and Properties of Human Hair Keratin Film Lacking Keratin-Associated Proteins

Human hair keratin film has been used as an alternative to hair samples to evaluate various damages. This film consisted of keratin and keratin-associated proteins (KAPs). The function of KAPs on the molecular constitution of hair and keratin film remains unclear. Recently, we have developed a selective isolation method for keratin and KAPs from human hair. In this study, we proposed a novel keratin film lacking KAPs using the Pre-cast method. The concentration of acetic acid in the casting solution of hair protein solution was higher than that in hair protein solution lacking KAPs. The morphology and chemical properties of the KAPs free keratin film were compared with those of conventional and high acetic acid keratin films containing KAPs. The KAPs free and high acetic acid films were beige and semitransparent in appearance, whereas the conventional film was white and opaque appearance. SEM observation indicated the KAPs free film was made up reticular structure and the surface was covered by small particles around 1 μm in diameter. When these films were stained with oxidative hair color reagents, color deposits of the KAPs free and high acetic acid films were higher than that of the conventional film. Compared with hair sample, the formation of cysteic acid was significantly prompt in these keratin films. The amount of the KAPs free film was slightly lower than those of the conventional and high acetic acid keratin films. When reductive permanent reagent containing thioglycolic acid was added to these keratin films, the optical transmittance was decreased. And the decrease was recovered by oxidative permanent processing. The film formation technology will be useful to evaluate various functions under which keratin and KAPs were classified